1. Field of the Invention
The invention relates generally to inks that are capable of chemical eradication. More particularly, the invention relates to a gel or gel-like ink system that includes a dye that can be made substantially colorless upon the application of an oxidizing agent.
2. Brief Description of Related Technology
Eradicable ink systems generally include two components. One component is an aqueous ink that includes a dye typically a triarylmethane-that can be rendered substantially colorless when contacted with a substance such as a sulfite oxidizing agent or an amine. The second component is an aqueous eradicator fluid that includes a substance that can cause the dye to convert to a substantially colorless form. A user writes with the ink and, if correction is necessary, applies the eradicator fluid to the ink marking to decolorize the dye.
Aqueous inks used in eradicable ink systems have the disadvantage that they tend to leave a permanent mark when applied to fabrics such as clothes. In addition, aqueous ink instruments (e.g., pens and markers) used in an eradicable ink system can be prone to leakage and drying out.
Traditional non-gel inks that are used in ball-point pens typically include largely non-volatile organic solvents, such as benzyl alcohol, phenyl cellosolve, diethylene glycol monoethyl ether, dipropylene glycol, glycerin, and propylene glycol. Non-gelled ball-point pen inks tend to have a relatively high viscosity (e.g., greater than 10,000 centipose (cP)).
Triarylmethane dyes generally include a relatively hydrophilic counter-ion that renders the dye-insoluble in non-volatile organic solvents (e.g., Acid Blue 93 includes two sodium counterions). Thus, one of the problems associated with using an eradicable dye (e.g., a triarylmethane dye) in a typical ball-point ink formulation is the low solubility of triarylmethane dyes in the non-volatile organic solvents that are used in typical non-gelled ball-point ink systems.